DP83822I: Setting Restriction

Hi Jin,

To clarify, you're disabling auto-neg, and forcing the PHY to different combinations of 10/100 speed and full or half duplex, while leaving Leaving auto-MDIX on?

If you are disabling auto-negotiation, auto-MDIX should also be disabled. Also if you are forcing a speed on one PHY, you must also force the speed on the other PHY, or you may enable auto-negotiation on both PHYs.

Thank you,

Nikhil

Hello Nikhil,

At first, the condition

Auto Negotiation: Disable (100Mbps/10Mbps, full-duplex/ half-duplex settings are fixed. It doesn't mean different combination settings.)
Auto MDI / MDIX: Enable.

>If you are disabling auto-negotiation, auto-MDIX should also be disabled.

Could you let me know the reason why it cannot be set?

As far as I know,  Auto MDI / MDIX allows connection using either a cross cable or a straight cable.
When Auto Negotiation is disabled & Auto MDIX is enabled, I thought the connected devices send idle signals to each other to establish a link.

Any advice will be appreciated

Jin

Hi Jin,

If auto-negotiation is disabled, you may enable Robust Auto-MDIX. This will prevent a deadlock If link partners are configured to operational modes that are not supported by normal Auto MDI/MDIX mode. Robust auto-negotiation can be enabled through register 9.

Thank you,

Nikhil

Hello Nikhil,

Thanks for your reply.

Let me make sure your answer, step by step.

[Question]
Can the Ethernet PHY be used with the following settings?

The following settings do not seem to be available with other companies' Ethernet PHY.
I would like to confirm whether this restriction is a general restriction for the Ethernet PHY or a restriction specific to the manufacturer.

Auto Negotiation: disable (100Mbps/10Mbps, full-duplex/half-duplex settings are fixed. It doesn't mean different combination settings.)
Auto MDI / MDIX: enable

*As far as I know,  Auto MDI / MDIX allows connection using either a cross cable or a straight cable.
When Auto Negotiation is disabled & Auto MDIX is enabled, I thought the connected devices send idle signals to each other to establish a link.

[Answer]

DP83822 can accept its condition with Robust Auto-MDIX. Is my understanding Correct ?

>If auto-negotiation is disabled, you may enable Robust Auto-MDIX. This will prevent a deadlock If link partners are configured to operational modes that are not supported by normal Auto MDI/MDIX mode. Robust auto-negotiation can be enabled through register 9.

Does above sentence (underline) have typo ? I cannot find "robust auto-negotiation" on our data sheet.

Also, in general case with standard PHY (Not DP83822), If user disable auto-negotiation, auto-MDIX should also be disabled ??

Best Regards,

Jin

Hi Jin,

>If auto-negotiation is disabled, you may enable Robust Auto-MDIX. This will prevent a deadlock If link partners are configured to operational modes that are not supported by normal Auto MDI/MDIX mode. Robust auto-negotiation can be enabled through register 9.

Does above sentence (underline) have typo ? I cannot find "robust auto-negotiation" on our data sheet.

Nikhil>> Yes this is a typo. If you are disabling auto-negotiation, but still want to use the MDIX feature, you must use the robust auto-MDIX, which can be enabled through register 9.

Also, in general case with standard PHY (Not DP83822), If user disable auto-negotiation, auto-MDIX should also be disabled ??

Nikhil>> Yes in the general case, if you disable auto-negotiation, auto-MDIX should also be disabled.

Thank you,

Nikhil

Dear Nikhil

＞If auto-negotiation is disabled, you may enable Robust Auto-MDIX. This will prevent a deadlock If link partners are configured to operational modes that are

＞not supported by normal Auto MDI/MDIX mode. Robust auto-negotiation can be enabled through register 9.

Thank you for your support.

Would you le me know the followings.

(1)Would you let me know detail of deadlock? Does it mean that the network link does not become "link-up" in long time?

(2)Why the deadlock happen in the following settings?

Auto Negotiation: disable (100Mbps, 10Mbps, full-duplex, half-duplex settings are fixed)
Auto MDI / MDIX: valid